Operational efficiency and overall output of a gas turbine engine generally increases as the temperature of the hot combustion gas stream increases. High combustion gas stream temperatures, however, may produce high levels of nitrogen oxides and other types of regulated emissions. A balancing act thus exists between operating a gas turbine engine in an efficient temperature range while also ensuring that the output of nitrogen oxides and other types of regulated emissions remain below mandated levels.
Lower emission levels of nitrogen oxides and the like may be promoted by providing for good mixing of the fuel stream and the air stream prior to combustion. Such premixing tends to reduce combustion temperatures and the output of nitrogen oxides. One method of providing such good mixing is through the use of a micro-mixer combustion nozzle wherein the fuel and the air are mixed in a number of micro-mixer tubes within a plenum before combustion.
Although current micro-mixer nozzle designs provide improved combustion performance, manufacturing such a micro-mixer nozzle may be challenging. As described above, the micro-mixer nozzle generally includes a number of small tubes with a number of small holes therein. Such components may require tight tolerances and hence may be time consuming to manufacture. Moreover, overall flow distribution may be difficult to control therein.
There is such a desire for an improved micro-mixer combustion nozzle design. Such an improved micro-mixer combustion nozzle design may promote good fuel/air mixing while providing ease of manufacturing, configuration, and use with lower cost components and techniques.